Seismic Design Of Mining Excavated Underground Metro Structure Considering Construction Process

China's subway is developing rapidly,and the total length of the subway will reach 10,000 kilometers by 2020.The earthquake damage cases of underground engineering at home and abroad make the engineers gradually realize the importance of seismic design of underground structure.Based on plaxis2d finite element software,this paper studies the seismic combination internal force design of underground metro stations.In this paper,the seismic responses on linings of a two-floors-three-span subway station is studied,in two cases with excavation process considered and not.In the case considering the excavation,there is a great influence on the design value of bending resistance of several important members of the structure,especially when the subway station is constructed in a hard soil environment.This paper mainly studies the seismic design method of underground subway station structure through numerical simulation analysis.The main research contents and results are as follows:(1)The influence of excavation process on the design of lining internal force in seismic combination of underground excavated subway station structure is studied.The calculation,comparison and analysis of two different seismic design methods considering excavation conditions and not considering excavation conditions are carried out.The results show that the harder the formation is the greater the influence of the excavation process will be.This effect is reflected in the design value of the internal forces of such important components as vault,side wall and floor.Therefore,seismic design should pay attention to the simulation of excavation process,especially in hard strata.(2)In the seismic design of underground station with excavation,the influence of the design calculation of primary lining and secondary lining on the seismic load combination design value of secondary lining is explored,and the following conclusions are drawn:the initial support of the arch has little influence on the seismic design of secondary lining moment and shear force of the arch,but has great influence on the seismic design of secondary lining axial force of the arch.The aseismic internal force design of the secondary lining of the side wall decreases with the increase of the proportion of the initial support included in the calculation,among which the influence on the bending moment and shear force design is small,and the influence on the axial force design is large.The inclusion of initial support has little influence on the design value of seismic internal force of floor and column.(3)Based on the failure analysis of underground excavated subway station with three spans and two floors,it is concluded that the failure places of the components in the structure are the middle plate,side arch roof,side wall,middle column and bottom plate successively.At the same time,the displacement Angle between the elastic and plastic layers of the structure is calculated when the middle plate is destroyed first and the structure is destroyed finally.The results show that the displacement Angle between the elastic and plastic layers of the structure just exceeds the limit value of the displacement Angle between the layers.